1. Field of the Invention
The present invention relates to valve devices responsive to an upsurge in flow rate to throttle or shut off the flow.
2. Description of the Prior Art
Natural gas is recognized as a relatively clean and inexpensive fuel source. Distribution systems are typically installed as part of a metropolitan or residential infrastructure to supply gas to the end users. Typically, a main gas line is laid and branch lines fed off the main line to the sites for individual gas meters, appliances, and the like. Natural gas is recognized as having high flammability such that uncontrolled escape thereof by rupture of the gas pipe line or branch line can create an extremely hazardous situation. An escape of natural gas into a confined space and exposure to any spark or any other ignition source can create an extremely volatile explosion.
In recognition of this fact, numerous different excess flow shut off valves have been proposed and are intended to be responsive to a abnormal surge in gas flow to close or throttle to thus minimize or stop gas flow. Typical of prior excess flow control valves are poppets biased to an open position by an internal coil spring which is responsive to a sudden pressure drop to discontinue flow. Such devices are made up of multiple machined components rendering them relatively expensive and often times provide a rather circuitous flow path, sometimes occupied in part by a coil spring which may hinder flow or otherwise add to the turbulence of flow thereby creating an unwanted pressure drop during normal operation.